This invention relates to a power gas burner, such as for use in a water heater or other appliance.
Various power gas burner assemblies are known, and two such assemblies are shown in U.S. Pat. Nos. 3,820,943 and 4,424,793. In these patents, primary air is mixed with gas at a point upstream of a flame retention head or plate. U.S. Pat. No. 3,820,943 discloses a pilot flame assembly, also located upstream of the flame retention plate, for igniting mixed gas and primary air prior to its discharge radially outwardly onto the outer surface of the plate, where the ignited gas and primary air then mixes with secondary air passing through the plate. U.S. Pat. No. 4,424,793 shows gas mixing with primary air in the throat of a venturi, which has its outlet disposed at the center of the flame retention plate. A spark igniter ignites the primary air-fuel mixture near the plate, whereafter the ignited mixture propogates outwardly and mixes with secondary air passing through the flame retention plate downstream thereof.
Various other burner structures are known in which gas is mixed with primary air in a chamber, which is in communication with a main burner casting disposed within a nozzle. A pilot assembly is provided adjacent the main burner casting for igniting the mixed gas and primary air upon discharge from the main burner casting. Secondary air passes through the nozzle surrounding the main burner casting and mixes with the ignited gas and primary air downstream of the nozzle.
The present invention provides a power gas burner of simple construction which provides a high degree of safety during operation. In accordance with the invention, a power gas burner assembly includes a housing having an air inlet and an air outlet, and a blower for providing pressurized air to the air inlet. A plate is adapted for placement at the air outlet, and includes a plurality of openings formed therein for outletting air from the housing. Gas supply means includes a gas outlet disposed downstream of the plate, so that gas discharged therethrough is mixed with air passing through the openings in the plate at a location downstream of the plate. Ignition means is located downstream of the plate for igniting mixed air and gas. With this construction, there is no pre-mixing of air and gas at a location upsteam of the plate, thereby avoiding flame flashback through the plate. In a preferred embodiment, the gas supply means comprises a gas tube extending through the housing and through the plate, with the plate acting to maintain the gas tube in position relative to the housing. The housing preferably comprises a tubular member with the air inlet located in a side thereof, with one end of the tubular member comprising the air outlet and the other end of the tubular member being substantially sealed. The gas tube preferably extends through the other end of the tubular member, and a mounting plate is adapted for placement thereat for fixing the position of the gas tube relative to the tubular housing. The gas outlet of the gas supply means preferably includes diverter means for diverting the direction of flow of the gas discharged through the gas outlet. The diverter means preferably comprises an orifice member having a plurality of passages therethrough for discharging gas radially outwardly into the flow path of air passing through the openings in the plate for mixing the gas with air. The ignition means preferably comprises a hot surface igniter disposed within the flow path of mixed air and gas downstream of the plate for igniting the mixture. The hot surface igniter is preferably mounted to the plate.